Production and purification of fatty oils



Patented July 4, 1944 PRODUCTION AND PURIFICATION OF OILS Don SheldonBolley, Brooklyn, N. Y., assignor to National Lead Company, New York, N.Y., a corporation of New Jersey No Drawing. Application April 12, 1940,

Serial No. 329,303

6 Claims.

This invention relates to the production and/or purification of fattyoils by a process involving solvent extraction and subsequentprecipitation of the oil from the solution by cooling.

One object of the invention is to provide an improved method of freeingthe extracted fatty oil from the solvent. Another object of theinvention is to provide a method of removing coloring matter, oxidizedmaterial, phosphatides, etc., from the fatty oil. Still another objectis to provide a method for separating a fatty oil into various fractionsof different degrees of unsaturation. Other objects of the inventionwill become apparent as the description thereof proceeds.

By the term fatty oils as used herein and in the appended claims ismeant oils which are derived from fatty oil containing raw material ofvegetable or animal origin and which are regarded chemically to be theglycerol esters of high molecular weight aliphatic acids, eithersaturated or unsaturated and embrace the drying, semi-drying andnon-drying oils.

Fatty oils are, at present, produced from fatty oil containing rawmaterials of either vegetable or animal origin by cooking and allowingthe oil to settle out; by pressing, or by solvent extraction. Thepresent invention is concerned with improvements in the methodsinvolving solvent extraction. For the purpose of this description of thepresent invention a solvent process is considered tobe any process inwhich th fatty oil in the course of its preparation and/or purificationis dissolved in solvents and subsequently separated therefrom. Thus, ifthe oil is pressed from vegetable or animal material and subsequentlydissolved in solvents it is considered a solvent process and theimproved methods of the present invention are applicable thereto.

In the prior art, fatty oil is recovered from a solvent solution bydistillation of the solvent by the application of heat, vacuum, or bothheat and vacuum. Thus, the recovered fatty oil contains any non-volatileimpurities which may be contained in the solution whereas the solvent isrecovered substantially pure.

I have now found that when a solvent solution is sufliciently cooled, asby the use of artificial refrigeration, the fatty oil will precipitatesubstantially completely out of the solution in a practically pure stateas an easily fllterable solid mass which may be readily separated fromany contaminating impurities which remain dissolved in the solvent. Ihave further found, when cooling fatty oils of the drying andsemi-drying types according to the present invention, that at differenttemperatures various fractions of the oil diflering from each otherparticularly with respect to degree of unsaturation separate out of thesolution. Hence, the present invention provides a means for obtaining agreat variety of different oil fraction from the same fatty-oilcontaining raw material.

. I am aware that the prior art teaches that a portion ofthe saturatedfatty oils may be removed from the bulk ofthe fatty oils by chillingeither the oil itself or a solution thereof in a suitable solvent andsubsequently removing the precipitated solids by filtration. Wheresolvents are used the bulk of the oil is then recovered, according tothese prior art methods, by distilling the solvent, leaving thenon-volatile impurities in the fatty oil. In contradistinction to suchmethods, the present invention contemplates a precipitation of the bulkof the fatty oil in solid condition and the subsequent separationthereof from the solvent which contains the impurities by filtration.

Any solvent commonly used in extracting fatty oil from vegetable oranimal oil containing raw materials and which does not solidify at thetemperatures employed may be used in practicing the present inventions.Such solvents will include the coal tar derivatives, e. g. mineralspirits, petroleum derivatives, e. g. petroleum spirits, petroleumether, etc., natural derivatives, e. g. turpentine, the alcohols, e. g.methyl, ethyl, isopropyl, propyl, etc., the ketones, e. g. acetone,methyl-ethyl ketone, etc., the ethers, e. g. ethyl ether, etc., theacetates, e. g., ethyl acetate, etc., the halogenated parafflns, e. g.carbon tetrachloride, chloroform, etc. Since, the only requirements of asolvent for use in practicing the invention are: (1) that it be capableof dissolving the fatty oil, and (2) that it be substantiallynon-freezing, i. c. it will not solidify at the low temperaturesemployed, a wide choice of solvents is permitted without departing fromthe scope of the invention.

I have found that substantially all of the fatty oil in solvent solutionwill be precipitated when the solution is cooled to temperatures betweenabout 40 C. and -70 C. When drying oils, such as linseed oil, aretreated according to the present invention. the degree of unsaturationof such oils may be enhanced. For instance, I have found, that the moresaturated constituents of the drying oil tend to precipitate at highertemperatures, for instance, between about 20 C. and about 40 C. than themore unsaturated constituents. When linseed oil is treated at atemperature of about -65 C. over of the oil will be recovered in ahighly unsaturated condition. The present invention, therefore, byenhancing the degree of unsaturation is especially adapted for improvingthe drying qualities of drying oils.

The general preferred method of practicing my invention is first toextract the fatty oil from the vegetable or animal fatty 011 containingraw material by any suitable means, either with or without the use ofsolvents. Such methods may include Soxhlet extraction, continuousextraction, dissolving decanted oil, soaking, etc. If no solvent hasbeen employed the raw oil is dissolved in a solvent. The fatty oilsolution is filtered to remove suspended, insoluble material. Thesolution may then be cooled either to precipitate at once the bulk ofthe dissolved oil or to bring about fractional crystallization of theoil into portions of varying degrees of saturation. The oil isprecipitated in a solid, easily fllterable form, separated from theliquid solvent containing the dissolved impurities in any convenientmanner, as by decantation or filtration. The solid oil is then melted,and freed from any residual small amounts of solvent by knownprocedures. The separated remaining solvent may be purified bydistillation and the residual material recovered.

Example I Crushed fiaxseed is treated with warm acetone untilpractically all the linseed oil has been extracted Sufficient acetone isused so that the resulting solution will contain about linseed oil. Thesolution is cooled to C. and filtered. About 3% of the linseed oil, 1.e., the more saturated portion thereof will precipitate. The precipitatewill also contain waxes, phosphatides, saturated giycerides,mucilaginous materials, etc. This fraction is discarded or used as aby-product. The remaining solution is then cooled to 68 C. and filtered.This will remove from solution all but about 4% of the oil. The portionof the oil remaining in solution is composed mainly of coloring matter,oxidized material, etc. The acetone is recovered by distillation and theresidue may be considered a by-product.

The oil which precipitates out at 68 C. is the main fraction andconsists of about 92% of the total oily material in the seed. It isfreed if Example II A solution of 10% linseed oil in acetone is cooledto 38 C. and filtered, then the solution chilled to -75 C. and filtered.The following fractions were obtained.

I Precipitating Percent Iodine temp. weight number C'. .20 to -38 11.8121 38 to 75 85. 4 196 2. 8 191 1 Not precipitated. The iodine number oftotal oil in the seed was 186. Thus, the middle fraction contains a highpercentage of the total oil with an increased iodine number. Therefore,the oil has been fractionated, so that a large proportion of the oil hasan iodine number of 10 points higher than the total oil. This isconsidered an advantage when the oil is to be used as a paint vehicle.Further, the oil has been purified by this treatment. By choosing otherprecipitating temperatures, fractions of oil having higher or loweriodine numbers may be obtained.

Example III Tung oil is extracted from the tung apple with acetone. A10% solution of the oil is cooled to -65 C. At that temperature 96% ofthe tung oil has precipitated from the solution. After filtering andfreeing from the retained solvent, a very much lighter oil containingsubstantially no impurities is obtained than may be manufactured bypressing or extraction and distillation of the solvent.

Example IV Castor oil is extracted from the crushed castor bean using aquantity of acetone so that the resulting solution will contain 10%castor oil. The acetone 011 solution is then cooled to --65 C. and theprecipitated oil recovered as in the previous examples. 94% of the totalcastor oil is obtained in this manner which is lighter in color andpurer than is obtained by pressing.

It will be seen from the foregoing description and the illustrativeexamples given that my invention comprises broadly a method of purifyingfatty oils by refrigeration, and embraces a means for the 1ractionalcrystallization of fatty oils which contain saturated and unsaturatedconstituents whereby the relative proportion of unsaturated constituentsis raised while that of the saturated constituents is reduced.

I claim: 7

1. Method for the treatment of fatty oils containing saturated andunsaturated constituents which comprises cooling a solution of a fattyoil in a non-freezing solvent to a temperature at which the moresaturated constituents will precipitate out of solution, separating fromthe solution the precipitated more saturated constituents together withprecipitated impurities, and further cooling the solution to atemperature at which the major portion of the remaining more unsaturatedconstituents precipitate out of solution.

2. Method for th treatment of fatty oils containing saturated andunsaturated portions which comprises cooling a solution of a fatty oilin a non-freezing solvent to temperatures between about -20 C. and downto 40 C., separating from the solution the precipitated more saturatedconstituents together with precipitated impurities, further cooling thesolution to temperatures between 40 C., and down to about -70 C. untilthe major portion of the remaining'more unsaturated constituents areprecipitated out of solution and thereafter separating the precipitatedmaterial from the solvent.

3. Method for the production of highly unsaturated linseed oil whichcomprises extracting flaxseed with acetone, filtering the resultingsolution, cooling it to about -2 C., separating therefrom precipitatedsolids, further cooling the solution to about 68 C. and separating theprecipitated, highly unsaturated linseed oil from the solvent.

4. Method according to claim 1 in which the fatty oil treated is linseedoil.

5. Method according to claim 1 in which the fatty oil treated is tungoil.

6. Method according to claim 1 in which the fatty oil treated is castoroil.

DON SHELDON BOLLEY.

